Dynamic hitless resizing in optical transport networks

ABSTRACT

The invention relates to techniques for controlling a dynamic hitless resizing in data transport networks. According to a method aspect of the invention, a network connection comprises M tributary slots defined in a payload area of a higher order transport scheme of the data transport network and the method comprises the steps of receiving a connection resize control signal at each of the nodes along the path of the network connection; adding at each node along the path in response to the connection resize control signal a second set of N tributary slots to the first set of the M tributary slots, such that the network connection comprises M+N tributary slots; and increasing, after M+N tributary slots are available for the network connection at each node along the path, a transport data rate of the network connection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2009/074015, filed on Sep. 17, 2009, which is hereby incorporatedby reference in its entirety.

TECHNICAL FIELD

The invention relates to techniques for controlling a dynamic hitlessresizing in data transport networks. More specifically, the inventionrelates to hitless resizing in optical transport networks.

TECHNICAL BACKGROUND

In a telecommunications environment, data transport networks such asPlesiochronous Digital Hierarchy (PDH) networks, Synchronous DigitalHierarchy (SDH) networks or Synchronous Optical NETworks (SONET) areused for transporting data streams from 2 Mbit/s up to 10 Gbit/s, notonly for voice, but also for packet data. Such transport networks mayform a backbone for interconnecting network nodes in a communicationsnetwork or between communication networks. The Optical TransportNetworks (OTN) may be employed as data transport networks for the higherdata rates of 1 Gbit/s up to 100 Gbit/s, which can be achieved based onoptical transmission technologies.

The International Telecommunication Union (ITU) TelecommunicationStandardization Sector (ITU-T) provides recommendation G.709 as thestandardization reference for optical data transport networks andinterfaces. The G.709 standard specifies the optical transport hierarchyand the interfaces for optical networks of various kinds of networkarchitectures.

The data to be transported for a particular client service will beinserted into transport frames of a suitable hierarchical leveldepending on the required data rate (bandwidth). However, in general thebandwidth required for a particular client service will not exactly fitto the bandwidth provided for by a particular hierarchical level, i.e.the efficiency of bandwidth usage will be low. In order to provide moreefficient use of the available bandwidth, concepts have been developedaccording to which the client service data are to be inserted intoseveral identical transport frames of a lower hierarchical level. Inorder to be able to recover the data at the end, the association of themultiple transport frames with each other has to be represented in thedata transport network. The related concepts are commonly referred to as“Virtual concatenation” (VCAT) initially developed for SDH, see for anintroduction G.709, section 18.

The approach for providing flexible bandwidth connections through an OTNis “ODUflex”, see G.709 amd 3, rev 2. ODUflex supports the transport ofcircuit-based (CBR, Constant Bit Rate) clients as well as packet-based(GFP, Generic Framing Procedure) clients. The bandwidth of the networkODU (Optical Data Unit) connection can be adjusted according to thebandwidth needs of the client service.

A general problem for any existing connection passing through the datatransport network is dynamic resizing, in particular in the case oftransporting packet based data. The client service may have a dynamicbandwidth requirement, i.e. the bandwidth requirement varies with time.The serving network connection should be flexibly configured accordinglyin a hitless manner, i.e. there should be no packet loss when resizingthe connection.

The hitless issue cannot be achieved when considering a very simplesolution for resizing, namely terminating, in a first step, an existingconnection and initiating, in a subsequent step, a new one (with adifferent bandwidth). At the time when the first connection is alreadyterminated, but the second connection is not yet active, there willpresumably packets be lost for the client service. Invoking the secondconnection before terminating the first leads to a blocking, i.e. waste,of transport resources. Thus, more sophisticated concepts are requiredfor hitless resizing.

In the (SDH) VCAT framework, a concept termed “Link Capacity AdjustmentScheme” (LCAS) has been developed, see G.7402 and for its application inOTN G.709, section 18.3. Using LCAS, the bandwidth of a “connection”represented by multiple virtually concatenated containers (ODUk) can beincreased or decreased by adding or removing elements of the VirtualConcatenation Group (VCG).

While the VCAT/LCAS approach provides for flexible bandwidth connectionswhich can be dynamically resized on demand, this comes on the cost ofhigh complexity. For example, the multiple members of the VCG may betransmitted along different paths in the network. Thus, delaycompensating buffers are required at the sink (egress) end point of thevirtual connection. Further, the LCAS protocol is relatively complex,as, for example, the status of each member has to be sent back from thesink end point to the source (ingress) end point of the virtualconnection.

SUMMARY

There is a demand for a technique for resizing a network connection in adata transport network, which enables hitless resizing with lesscomplexity.

This demand is satisfied by a first method for controlling dynamichitless resizing of a network connection in a data transport network.All the method aspects and node aspects outlined in this section arebased on that a path of the network connection extends between twoconnection end nodes and optionally over one or more intermediate nodesof the data transport network. The network connection transports data ofclient services in transport frames from the ingress end node to theegress end node. The network connection comprises a first set of Mtributary slots defined in a payload area of a higher order transportscheme of the data transport network.

The first method comprises, in case the network connection is to beincremented, the steps of receiving a connection resize control signalat each of the nodes along the path of the network connection; adding ateach node along the path in response to the connection resize controlsignal a second set of N tributary slots to the first set of the Mtributary slots (after increasing, M+N tributary slots are available forthe network connection at each node along the path); and increasing,after M+N tributary slots are available for the network connection ateach node along the path and in a synchronized manner between each pairof neighboring nodes, a transport data rate of the network connection.In case the network connection is to be decremented, the first methodcomprises the steps of receiving a connection resize control signal ateach of the nodes along the path of the network connection; decreasing,after a second set of N tributary slots has been prepared for removal ateach node along the path of the network connection in a synchronizedmanner between each pair of neighboring nodes, a transport data rate ofthe network connection; and removing at each node along the path inresponse to the connection resize control signal a second set of Ntributary slots from the first set of the M tributary slots (thus, afterdecreasing, M−N tributary slots are available for the network connectionat each node along the path).

The data transport network may comprise an optical transport network. Inone variant, the network connection is an Optical Channel Data Unit“ODU” connection with selectable bandwidth. Specifically, the networkconnection may be an ODUflex connection.

In one implementation, the network connection comprises a set of linkconnections between each pair of neighboring nodes along the path, andcomprises matrix through-connections in each intermediate node in thepath, a matrix internally interconnecting multiple link connections ofthe intermediate node with other nodes in the data transport network,link connections and matrix through-connections being defined based onthe tributary slots. Each node along the path of the network connectioncomprises at least on collection/distribution point for eithercollecting the client data from a set of link connections anddistributing the client data to a set of matrix through-connections orfor collecting the client data from a set of matrix through-connectionsand distributing the client data to a set of link connections. In casethe network connection is to be incremented, the step of adding the Ntributary slots comprises, at the collection/distribution point, addingthe N tributary slots to the M link connections, and adding the Ntributary slots to the M matrix through-connections. In case the networkconnection is to be decremented, the step of removing the N tributaryslots comprises, at the collection/distribution point, removing the Ntributary slots from the M link connections, and removing the Ntributary slots from the M matrix through-connections.

According to one implementation, the method may comprise the furthersteps of sending, by the ingress end node, a data rate control signalhop-by-hop along the path of the network connection, wherein the datarate control signal is discarded by a node which has not finished thestep of adding or making for removal, respectively, the N tributaryslots; sending, by the egress end node in response to a reception of thedata rate control signal, an acknowledgement to the ingress end node;and increasing, in case the network connection is to be incremented, bythe ingress end node in response to the reception of the acknowledgementthe data rate of the signal passing through the network connection; orin case the network connection is to be decremented, decreasing the datarate of the signal passing through the network connection and thenremoving the N tributary slots from the M tributary slots at each nodealong the path.

Thus, the data rate control signal and the acknowledgement thereofrepresent a form of handshaking procedure between the end nodes.

The data rate signal may comprise N TS signals, each TS signal beingsent separately hop-by-hop along the path and being acknowledgedseparately by the egress end node.

In one realization of the method, the step of adding or removing,respectively, the second set of N tributary slots to or from the firstset of the M tributary slots in an intermediate node comprises adding orremoving, respectively, the N tributary slots to or from the M tributaryslots with respect to at least a link connection, the link connectionconnecting the intermediate node with another node along the path of thenetwork connection, and a matrix through-connection, the matrixinternally interconnecting multiple link connections of the intermediatenode with other nodes in the data transport network; and re-grouping, incase M tributary slots are assigned to the link connection and M+Ntributary slots are assigned to the matrix through-connection, or incase M+N tributary slots are assigned to the link connection and Mtributary slots are assigned to the matrix through-connection, the datato be transported over the network connection from M data groups intoM+N data groups or from M+N data groups into M data groups, or,alternatively, re-grouping, in case M tributary slots are assigned tothe link connection and M−N tributary slots are assigned to the matrixthrough-connection, or in case M−N tributary slots are assigned to thelink connection and M tributary slots are assigned to the matrixthrough-connection, the data to be transported over the networkconnection from M data groups into M−N data groups or from M−N datagroups into M data groups.

According to a one implementation, the step of adding the N tributaryslots to the M tributary slots in a node may comprise decreasing anumber of data units per transport frame for the M tributary slots by afactor of M/(M+N), or alternatively the step of removing the N tributaryslots from the M tributary slots in the node comprises increasing anumber of data units per transport frame for the M tributary slots by afactor of M/(M−N).

In this implementation, a number of data units per transport frame forthe N tributary slots may be kept unchanged. In the step of increasingor decreasing, respectively, the transport data rate of the networkconnection, a number of data units per transport frame may be increasedor decreased, respectively, collectively for the M tributary slots andthe N tributary slots.

The connection resize control signal may be sent by network management,and may be sent in arbitrary order to each of the nodes along the pathof the network connection. The step of adding or removing, respectively,the N tributary slots to or from the M tributary slots may be performedin each of the nodes along the network connection path independently.

One realization of the method comprises, for the case that the Ntributary slots are to be added to the M tributary slots, the previoussteps of checking an availability of N tributary slots in each of thenodes along the path of the network connection; and allocating availableN tributary slots in the nodes along the path for the networkconnection.

At least one of the connection resize control signal and the data ratecontrol signal may be transported in an overhead portion of at least oneof the second set of the N tributary slots. The at least one of thesecond set of the N tributary slots may have been allocated in theallocating step but may be unused prior to the step of increasing thetransport data rate of the network connection. Alternatively, the slotis to be unallocated in a subsequent de-allocation step in case thenetwork connection has to be decremented, and is therefore alreadyunused.

The above-mentioned demand is further satisfied by a second method forcontrolling dynamic hitless resizing of a network connection in a datatransport network. The method is performed in the ingress end node. Forthe case the network connection is to be incremented, the second methodcomprises the steps of receiving a connection resize control signal;adding a second set of N tributary slots to the first set of the Mtributary slots (after increasing, M+N tributary slots are available forthe network connection at each node along the path); and increasing,after M+N tributary slots are available for the network connection ateach node along the path and in a manner synchronized with thedownstream node, a transport data rate of the network connection. Incase the network connection is to be decremented, the second methodcomprises the steps of receiving (314) a connection resize controlsignal; decreasing, after a second set of N tributary slots has beenprepared for removal in a synchronized manner between the ingress endnode and the neighboring node, a transport data rate of the networkconnection; and removing a second set of N tributary slots from thefirst set of the M tributary slots (after decreasing, M−N tributaryslots are available for the network connection at each node along thepath).

One implementation of the second method comprises the further steps ofinitiating a sending of a data rate control signal hop-by-hop along thepath of the network connection, wherein the data rate control signal isdiscarded by a node which has not finished the step of adding or markingfor removal, respectively, the N tributary slots; and receiving anacknowledgement to the data rate control signal from the egress endnode; and increasing, in case the network connection is to beincremented, in response to the reception of the acknowledgement thedata rate of the signal passing through the network connection; or, incase the network connection is to be decremented, decreasing the datarate of the signal passing through the network connection and thenremoving the N tributary slots from the M tributary slots at each nodealong the path.

The above-mentioned demand is still further satisfied by a third methodfor controlling dynamic hitless resizing of a network connection in adata transport network. The method is performed in an intermediate nodeand comprises the steps of receiving a connection resize control signal;adding or removing, respectively, in response to the connection resizecontrol signal a second set of N tributary slots to or from the firstset of the M tributary slots, such that the network connection comprisesM+N tributary slots or M−N tributary slots, respectively.

In one implementation, the network connection comprises a set of linkconnections between each pair of neighboring nodes along the path, andcomprises matrix through-connections in each intermediate node in thepath, a matrix internally interconnecting multiple link connections ofthe intermediate node with other nodes in the data transport network,link connections and matrix through-connections being defined based onthe tributary slots. The intermediate node comprises a firstcollection/distribution point for collecting the client data from a setof link connections terminating from the upstream node and distributingthe client data to a set of matrix through-connections and a secondcollection/distribution point for collecting the client data from a setof matrix through-connections and distributing the client data to a setof link connections starting towards a downstream node. In case thenetwork connection is to be incremented, the step of adding the Ntributary slots comprises, at each of the collection/distribution point,adding the N tributary slots to the M link connections, and adding the Ntributary slots to the M matrix through-connections. In case the networkconnection is to be decremented, the step of removing the N tributaryslots comprises, at each of the collection/distribution points, removingthe N tributary slots from the M link connections, and removing the Ntributary slots from the M matrix through-connections.

According to one variant, the third method comprises the further stepsof receiving a data rate control signal from a node upstream ordownstream the network connection path; and discarding the data ratecontrol signal in case the step of adding or marking for removal,respectively, the N tributary slots is not finished, or alternativelyforwarding the data rate control signal to the next node along thenetwork connection path.

In one implementation of the third method, the step of adding orremoving, respectively, the N tributary slots to or from the M tributaryslots comprises adding or removing, respectively, the N tributary slotsto or from the M tributary slots with respect to either a linkconnection, the link connection connecting the intermediate node withanother node along the path of the network connection, or a matrixthrough-connection, the matrix internally interconnecting multiple linkconnections of the intermediate node with other nodes in the datatransport network; and re-grouping, in case M tributary slots areassigned to the link connection and M+N tributary slots are assigned tothe matrix through-connection, or in case M+N tributary slots areassigned to the link connection and M tributary slots are assigned tothe matrix through-connection, the data to be transported over thenetwork connection from M data groups into M+N data groups or from M+Ndata groups into M data groups, or, alternatively, re-grouping, in caseM tributary slots are assigned to the link and M−N tributary slots areassigned to the matrix through-connection, or in case M−N tributaryslots are assigned to the link connection and M tributary slots areassigned to the matrix through-connection, the data to be transportedover the network connection from M data groups into M−N data groups orfrom M−N data groups into M data groups.

The above-mentioned demand is also satisfied by a fourth method forcontrolling dynamic hitless resizing of a network connection in a datatransport network. The method is performed in the egress end node andcomprises the steps of receiving a connection resize control signal;adding or removing, respectively, in response to the connection resizecontrol signal a second set of N tributary slots to or from the firstset of the M tributary slots; such that the network connection comprisesM+N tributary slots or M−N tributary slots, respectively; receiving adata rate control signal from the node upstream the network connectionpath; and sending, in response to a reception of the data rate controlsignal, an acknowledgement to the ingress end node.

Further, the abovementioned demand is satisfied by a computer programproduct, which comprises program code portions for performing the stepsof one or more of the methods and method aspects described herein whenthe computer program product is executed on one or more computingdevices, for example an ingress end node, intermediate node, or egressend node of a network connection in a data transport network. Thecomputer program product may be stored on a computer readable recordingmedium, such as a permanent or re-writeable memory within or associatedwith a computing device or a removable CD-ROM, DVD or USB-stick.Additionally or alternatively, the computer program product may beprovided for download to a computing device, for example via a datanetwork such as the Internet or a communication line such as a telephoneline or wireless link.

Further, the above-mentioned demand is satisfied by a network nodeadapted for controlling dynamic hitless resizing of a network connectionin a data transport network. The network node implements the ingress endnode and comprises a component adapted to receive a connection resizecontrol signal; a component adapted to add a second set of N tributaryslots to the first set of the M tributary slots; a component adapted toincrease, after M+N tributary slots are available for the networkconnection at each node along the path and in a synchronized mannerbetween each pair of neighboring nodes, a transport data rate of thenetwork connection; a component adapted to decrease a transport datarate of the network connection, after a second set of N tributary slotshas been prepared for removal at each node along the path of the networkconnection in a synchronized manner between each pair of neighboringnodes; and a component adapted to remove a second set of N tributaryslots from the first set of the M tributary slots.

The network node may further comprise a component adapted to initiate asending of a data rate control signal hop-by-hop along the path of thenetwork connection, wherein the data rate control signal is discarded bya node which has not finished the step of adding or marking for removal,respectively, the N tributary slots; a component adapted to receive anacknowledgement to the data rate control signal from the egress endnode; a component adapted to increase, in response to the reception ofthe acknowledgement, the data rate of the signal passing through thenetwork connection, and a component adapted to decrease, in case thenetwork connection is to be decremented, the data rate of the signalpassing through the network connection and a component adapted to thenremove the N tributary slots from the M tributary slots at each nodealong the path.

The above-mentioned demand is further satisfied by a network nodeadapted for controlling dynamic hitless resizing of a network connectionin a data transport network, wherein the network node implements anintermediate node. The network node comprises a component adapted toreceive a connection resize control signal; a component adapted to addor remove, respectively, in response to the connection resize controlsignal a second set of N tributary slots to or from the first set of theM tributary slots, such that the network connection comprises M+Ntributary slots or M−N tributary slots, respectively; and a componentadapted to forward the connection resize control signal to the next nodealong the network connection path.

According to one implementation, the network connection comprises a setof link connections between each pair of neighboring nodes along thepath, and comprises matrix through-connections in each intermediate nodein the path, a matrix internally interconnecting multiple linkconnections of the intermediate node with other nodes in the datatransport network, link connections and matrix through-connections beingdefined based on the tributary slots. The intermediate node comprises afirst collection/distribution point for collecting the client data froma set of link connections terminating from the upstream node anddistributing the client data to a set of matrix through-connections anda second collection/distribution point for collecting the client datafrom the set of matrix through-connections and distributing the clientdata to a set of link connections starting towards a downstream node.Each of the collection/distribution points is adapted to, in case thenetwork connection is to be incremented, add the N tributary slots byadding the N tributary slots to the M link connections, and adding the Ntributary slots to the M matrix through-connections. Each of thecollection/distribution points is adapted to, in case the networkconnection is to be decremented, remove the N tributary slots byremoving the N tributary slots from the M link connections, and removingthe N tributary slots from the M matrix through-connections.

In one variant, the network node further comprises a component adaptedto receive a data rate control signal from a node upstream or downstreamthe network connection path; and a component adapted to discard the datarate control signal in case the step of adding or marking for removal,respectively, the N tributary slots is not finished, and a componentadapted to forward the data rate control signal to the next node alongthe network connection path.

According to one implementation of the network node, the componentadapted to add or remove, respectively, the N tributary slots to or fromthe M tributary slots comprises a sub-component adapted to add orremove, respectively, the N tributary slots to or from the M tributaryslots with respect to either a link connection, the link connectionconnecting the intermediate node with another node along the path of thenetwork connection, or a matrix through-connection, the matrixinternally interconnecting multiple link connections of the intermediatenode with other nodes in the data transport network; and a sub-componentadapted to re-group, in case M tributary slots are assigned to the linkconnection and M+N tributary slots are assigned to the matrixthrough-connection, or in case M+N tributary slots are assigned to thelink connection and M tributary slots are assigned to the matrixthrough-connection, the data to be transported over the networkconnection from M data groups into M+N data groups or from M+N datagroups into M data groups, or, additionally or alternatively, beingadapted to re-group, in case M tributary slots are assigned to the linkconnection and M-N tributary slots are assigned to the matrixthrough-connection, or in case M−N tributary slots are assigned to thelink connection and M tributary slots are assigned to the matrixthrough-connection, the data to be transported over the networkconnection from M data groups into M−N data groups or from M−N datagroups into M data groups.

The above-mentioned demand is still further satisfied by a network nodeadapted for controlling dynamic hitless resizing of a network connectionin a data transport network, wherein the network node implements theegress end node and comprises a component adapted to receive aconnection resize control signal; a component adapted to add or remove,respectively, in response to the connection resize control signal asecond set of N tributary slots to or from the first set of the Mtributary slots, such that the network connection comprises M+Ntributary slots or M−N tributary slots, respectively; a componentadapted to receive a data rate control signal from the node upstream thenetwork connection path; and a component adapted to send, in response toa reception of the data rate control signal, an acknowledgement to theingress end node.

The above-mentioned demand is eventually satisfied by a data transportnetwork comprising one or more of the network nodes as outlined above.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will further be described with referenceto exemplary embodiments illustrated in the figures, in which:

FIG. 1 a schematically illustrates an embodiment of an optical transportnetwork;

FIG. 1 b illustrates more details of the ODUflex connection extendingover the network of FIG. 1 a;

FIG. 2 schematically illustrates functional blocks of the ingress endnode illustrated in FIG. 1 a;

FIG. 3 a is a flow diagram illustrating a first operational mode of theingress end node of FIG. 2;

FIG. 3 b is a flow diagram illustrating a second operational mode of theingress end node of FIG. 2;

FIG. 4 schematically illustrates functional blocks of an embodiment ofone of the intermediate nodes illustrated in FIG. 1 a;

FIG. 5 a is a flow diagram illustrating an operation of the intermediatenode of FIG. 4;

FIG. 5 b illustrates in more detail one of the steps of the flow diagramof FIG. 5 a;

FIG. 6 schematically illustrates functional blocks of an embodiment ofthe egress end node illustrated in FIG. 1 a;

FIG. 7 is a flow diagram illustrating an operation of the egress endnode of FIG. 1 a;

FIG. 8 illustrates an overall operation for incrementing the networkconnection of the network of FIG. 1 a;

FIG. 9 illustrates an overall operation for decrementing the networkconnection of the network of FIG. 1 a;

FIG. 10 is a flow diagram illustrating an overall operation forincrementing the network connection of the network of FIG. 1 a;

FIG. 11 is a flow diagram illustrating an overall operation fordecrementing the network connection of the network of FIG. 1 a;

FIG. 12 schematically illustrates a signaling format for controlling ahitless resizing;

FIGS. 13 a-13 l schematically illustrate step-by-step a process ofincreasing the network connection in the network of FIG. 1 a; and

FIGS. 14 a-14 m schematically illustrate step-by-step a process ofdecreasing the network connection in the network of FIG. 1 a.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific examples of network scenarios, network nodes andoperations thereof will be set forth in order to provide a thoroughunderstanding of the current invention. It will be apparent to one ofskill in the art that the current invention may be practiced inembodiments that depart from these specific aspects.

Those skilled in the art will further appreciate that functionsexplained herein below may be implemented using individual hardwarecircuitry, using software functioning in conjunction with a programmedmicroprocessor or a general purpose computer, using an applicationspecific integrated circuit (ASIC) and/or using one or more digitalsignal processors (DSPs). It will also be appreciated that when thecurrent invention is described as a method, it may also be embodied in acomputer processor and a memory coupled to the processor, wherein thememory is encoded with one or more programs that perform the methodsdisclosed herein when executed by the processor.

FIG. 1 illustrates an embodiment of an optical transport network 100which comprises network nodes 102, 104, 106 and 108. Between particularpairs of nodes, specific data transmission capacities are available, asindicated schematically for the pair of nodes 102 and 104 by link 110,for the pair of nodes 104 and 106 by link 112, and for the pair of nodes106 and 108 by link 114. An ODUflex connection 116 extends over network100. With respect to the ODUflex connection 116, node 102 is the ingress(source) end node, nodes 104 and 106 are intermediate nodes, and node108 is the egress (sink) end node.

FIG. 1 b illustrates in more detail the ODUflex connection 116 asrepresented, for example, in the link 110. The link 110 comprises a HOODUk (Higher Order Optical Data Unit level k) with a fixed number oftributary slots (TS) 118, the number thereof being determined by thelevel k. The ODUflex network connection 116 comprises M of the tributaryslots 118, M being a natural number. The links 112 and 114 may show asimilar structure.

FIG. 2 schematically illustrates functional building blocks of anembodiment of the ingress end node 102 of FIG. 1 a. The node 102comprises a framing component 202, a mapping component 204, a ConnectionResize Control (CRC) component 206 and a Data Rate Control (DRC)component 208. The framing component 202 is adapted to insert clientdata 210 (e.g., Ethernet, MPLS, or IP) into the M tributary slots (TS)212 configured to form the ODUflex connection 116. For example, theclient data packets are encapsulated in an OPUflex payload area. TheMapping component 204 acts to manage the ODUflex connection 116 in theingress end node 102.

The node 102 is also adapted to control a dynamic hitless resizing ofthe ODU connection 116. Corresponding operations of node 102 will bedescribed with respect to the flow diagrams illustrated in FIGS. 3 a and3 b. Referring first to FIG. 3 a, in step 302, the CRC component 206 isoperative to receive a connection resize control signal, which may besent from a network management entity. The connection resize control(CRC) signal indicates to the node the resizing of the ODUflexconnection 116. For example, one connection resize control signal may besent containing data for all TSs to be added to the connection 116, andsuch control signal may indicate a port number of each slot.

The CRC component 206 may receive the CRC signal 214. The CRC component206 controls the further components of the node 102 accordingly, as willbe described below.

In step 304, the mapping component 204 adds a second set of N tributaryslots 216 to the first set of the M tributary slots 212. The CRCcomponent 206 may instruct the mapping component 204 to reconfigure theN tributary slots 216 according to the information received in thesignaling 214.

In step 306, the DRC component 208 is triggered by the CRC component 206to generate a Data Rate Control (DRC) signal (one DRC signal for each ofthe N slots to be added). The DRC signal is discarded by any node alongthe path of the ODUflex connection 116 which has not yet finished thestep of adding or marking for removal, respectively, the particular slotof the N tributary slots. In other words, in case the DRC signal isconveyed hop-by-hop along the path of connection 116, the DRC signalwill only arrive at the egress end node 108 after the ingress end node102 and all intermediate nodes 104, 106 have successfully resized theODUflex connection by adding or removing the particular of the N slotsto or from the M slots. The DRC component 208 provides the DRC signal tothe framing component 202 and initiates thereby the sending of the DRCsignal hop-by-hop along the path of the network connection 116, as theDRC signal may be conveyed in the overhead of transport frames (moredetails will be given below).

In step 308, from the egress end node 108 an acknowledgement to the DRCsignal of step 306 is received in node 102 (not explicitly shown in FIG.2). In response thereto, in step 310 the transport data rate of thesignal passing through the ODUflex connection 116 is increased bysuitable operation of at least one the framing component 202 and mappingcomponent 204. For example, in case of incrementing the ODUflexconnection 116, after M+N tributary slots are available for theconnection 116 at each node along the path, the transport data rate isincreased. Alternatively, in case the ODUflex connection 116 has to bedecremented, the data rate of the signal passing through the networkconnection 116 is decremented. Then the N tributary slots are removedfrom the M tributary slots.

The step of preparing the N slots for either addition or removal in eachnode has to be synchronized with the neighboring node on the other endof the link connection in order to ensure that it is the same tributaryslot or set of tributary slots which is removed on both ends of the linkconnection.

FIG. 3 b illustrates, in a similar manner as FIG. 3 a, a procedure ofcontrolling a decrementing of a network connection. In step 312, the CRCcomponent 206 receives a CRC signal from network management. In step314, the framing component 202 and/or mapping component 204 is operativeto decrease a transport data rate of the network connection 116. In step316, the mapping component 204 removes N tributary slots from the Mtributary slots.

FIG. 4 schematically illustrates functional building blocks of anembodiment of the intermediate node 104 (or 106) of FIG. 1 a. The node104 comprises an upstream mapping component 402, downstream mappingcomponent 404, a Matrix 406, a Connection Resize Control (CRC) component408 and a Data Rate Control (DRC) component 410. The upstream mappingcomponent 402 is adapted to manage M tributary slots 412 of ODUflexconnection 116 in the direction to the ingress end node 102, while thedownstream mapping component 404 is adapted to manage M tributary slots414 of ODUflex connection 116 in the direction to the egress end node108. The Matrix 406 is for interconnecting the various data inputs anddata outputs of node 104.

Each of the mapping components comprises a collection/distribution point(CDP, not explicitly drawn). With regard to the mapping component 402,the CDP thereof is configured for collecting the client data from theset of link connections 412 of network connection 116 terminating fromthe upstream node 102 and distributing the client data further to a setof matrix through-connections (not explicitly drawn). With regard to themapping component 404, the CDP thereof is configured for collecting theclient data from the set of matrix through-connections and distributingthe client data to the set of link connections 414 starting towards thedownstream node 106.

The node 104 is also adapted to control a dynamic hitless resizing ofthe ODU connection 116. A corresponding operation of node 104 will bedescribed with respect to the flow diagram illustrated in FIG. 5 a. Instep 502, the CRC component 206 is operative to receive a connectionresize control (CRC) signal from network management. The component 408uses the signal to accordingly control mapping component 402 and 404,for example.

In step 504, each of the mapping components 402 and 404 is triggered bythe CRC component 408 (in response to the CRC signal) to add or remove,respectively, a second set of N tributary slots 416 and 418,respectively, to or from the first set of the M tributary slots 412 and414, respectively. Thus, the network connection comprises M+N tributaryslots or M−N tributary slots, respectively. Some synchronization isperformed between the node and neighboring nodes for the addition orremoval of the N tributary slots in order to ensure that slots are addedor removed belonging to the same link connection on both ends of eachlink connection.

In step 506, the DRC component 410 is operative to receive a data ratecontrol (DRC) signal from a neighbor node of the network connection path116 (in-band signaling is conveyed downstream in the examplesillustrated here, i.e., the neighbor node is an upstream node, which isin case of node 104 the ingress end node 102 illustrated in FIGS. 2 and3). In step 508, the DRC component 410 determines from the mappingcomponents 402 and 404 whether or not the process initiated in step 504of adding or marking for removal, respectively, the N tributary slots isfinished already. If this is not yet the case, the DRC component 410operates to discard the DRC signal. For example, in case the DRC signalis that a particular bit in an OH portion of a transport frame is set,then the DRC signal may be discarded by unsetting the bit (andforwarding the unset bit to the next hop along the path). If the processof adding or marking for removal the N TS has already been finished, theDRC component may keep the DRC signal, e.g. a set bit may be kept as aset bit. Then the DRC component 410 may forward the DRC signal as it isto the next node along the network connection path 116.

FIG. 5 b illustrates in more detail the operations taken in step 504.While the steps illustrated in FIG. 5 b apply to both the mappingcomponents 402 and 404, for the sake of conciseness only the operationof mapping component 402 will be explicitly described, while mappingcomponent 404 operates in a similar way. In sub-step 512, the mappingcomponent 402 adds or removes, respectively, the N tributary slots 416to or from the M tributary slots 412. The mapping component does so withrespect to at least one of the link 110 and the matrix 406, moreprecisely the through-connection of the tributary slots 412 (andpossibly 416) related to the ODUflex connection 116 over the matrix 406.

The step 514 relates to the situation at a particular point in timethat, for example, only the M tributary slots 412 are assigned to thelink 110 (the N TS 416 have not yet been assigned or have beende-assigned already) and M+N tributary slots are assigned to the matrixthrough-connection. The step 514 also relates to the situation that M+Ntributary slots are assigned to the link (i.e. the N TS have beenassigned already in case the ODUflex connection 116 has to beincremented or have been not yet been de-assigned in case the ODUflexconnection 116 has to be decremented) and M tributary slots are assignedto the matrix through-connection. For these cases, a re-groupingfunction 420 (422) or M:(M+N) process is provided which operates suchthat the data to be transported over the ODUflex connection 116 arere-grouped from M data groups into M+N data groups or from M+N datagroups into M data groups, respectively. For example, groups of MODUflex bytes are re-grouped into groups of M+N ODUflex bytes (or viceversa).

In an alternative situation (not depicted in the figures), a stepsimilar to step 514 may relate to the situation at a particular point intime that, for example, only the M tributary slots 412 are assigned tothe link 110 and M−N tributary slots are assigned to the matrixthrough-connection. Such step may also relate to the situation that M−Ntributary slots are assigned to the link and M tributary slots areassigned to the matrix through-connection. For these cases, there-grouping function 420 (422) or M:(M+N) process may be adapted tooperate such that the data to be transported over the ODUflex connection116 are re-grouped from M data groups into M−N data groups or from M−Ndata groups into M data groups, respectively. For example, groups of MODUflex bytes are re-grouped into groups of M−N ODUflex bytes (or viceversa).

FIG. 6 schematically illustrates functional building blocks of anembodiment of the egress end node 108 of FIG. 1 a. The node 108comprises a mapping component 602, a de-framing component 604, aConnection Resize Control (CRC) component 606 and a Data Rate Control(DRC) component 608. The mapping component 602 acts to manage theODUflex connection 116 incoming from the upstream intermediate node 106.The de-framing component 604 is adapted to extract the client data 210(see FIG. 2) from the tributary slots 610 (or 610 and 612) contributingto the ODUflex connection 116. For example, client data packets may beextracted from an OPUflex payload area.

The node 108 is also adapted to control a dynamic hitless resizing ofthe ODU connection 116. A corresponding operation of node 108 will nowbe described with respect to the flow diagram illustrated in FIG. 7. Instep 702, the CRC component 606 operates to receive a connection resizecontrol (CRC) signal. In step 704, the CRC component 606 triggers, inresponse to the received CRC signal, the mapping component 602 to add orremove, respectively, the second set of N tributary slots 612 to or fromthe first set of M tributary slots 610. Thus, the network connectioncomprises M+N tributary slots or M−N tributary slots, respectively.

In step 706, the DRC component 608 acts to receive a data rate control(DRC) signal from the intermediate node 106. In step 708, the DRCcomponent 608 initiates, in response to the reception of the data ratecontrol signal, sending of an acknowledgement 614 to the ingress endnode 102.

In FIGS. 2 to 7 the dynamic hitless resizing of ODUflex connection 116has been described from the point of view of the end nodes 102, 108 andintermediate nodes 104, 106, respectively. As a general remark regardingthe synchronization of different nodes, ODUflex generally may use theclock of HO ODUk, or system clock, and this will also generally besufficient for the dynamic hitless resizing techniques described herein.

FIGS. 8 and 9 schematically illustrate the process of dynamic hitlessresizing from an overall network perspective. FIG. 8 is related toincrementing an ODUflex connection, while FIG. 9 illustrates the case ofdecrementing an ODUflex connection. In both embodiments, with changingbandwidth requirements first the ODUflex network connection carrying theODUflex signal is resized before resizing the ODUflex signal.

Turning first to the scenario of FIG. 8, initially the individualODUflex link connections and matrix connections are incremented (thiswill be more explicitly detailed in embodiments described furtherbelow). In detail, the Matrix Connection (MC) 1 and 2 are increased,then the Link Connections (LC) 2, 3, and 1 are increased. During thisprocess the ODUflex signal itself is kept unchanged. Only afterwards,the ODUflex signal (ODUflex_AI/CI) itself is increased. Once the ODUflexsignal is increased, its larger payload bandwidth is offered to thepacket layer.

With respect to FIG. 9, first a smaller payload bandwidth of the ODUflexsignal is enforced on the packet layer. Second, the ODUflex signal CI/AIis decremented. Third, the individual ODUflex link connections andmatrix connections are decreased. In the specific example illustrated inFIG. 9, the Link Connection LC1 is decreased first, then the MatrixConnection MC2 is decreased, then the Link Connections LC2 and LC3 aredecreased, and finally the Matrix Connection MC1 is decreased. Asillustrated by FIGS. 8 and 9, generally the resizing of individual linkconnection or matrix through-connections may be performed independent ofeach other.

It is to be understood that, taking a functional layer perspective,according to the techniques proposed herein a resizing of a networkconnection comprises a resizing of the Adaptation Information (AI) andthe Characteristic Information (CI), e.g. in the service layer, whilethe know VCAT/LCAS techniques merely comprise a resizing of AI, asaccording thereto a resizing comprises usage of M smaller CI to the useof (M+N) smaller CI. In other words, VCAT/LCAS resizing does notcomprises any change of existing links but only the addition of newlinks or removal of existing links.

FIG. 10 illustrates in more detail a procedure for controlling dynamichitless resizing, in particular incrementing, a network connection in adata transport network. In step 1002, an availability of N sparetributary slots (TS) is checked in each of the nodes along the path ofthe network connection. For example, network management may check theavailability of N spare tributary slots on LO ODU links and matricespassed through by the ODUflex network connection 116 depicted in theforegoing examples.

In step 1004, if N spare TS are available at each of the nodes (moreexplicitly, at each of the one or two connection/distribution points ofeach of the nodes), the available N tributary slots are allocated in thenodes along the path for the network connection. For example, Networkmanagement (e.g. directly or via a control plane mechanism) may allocatethose N tributary slots in each link and matrix through-connection tothe ODUflex connection in case there are enough spare tributary slots.As the allocation was successful, in step 1006, network management sendsa connection resize control signal to each of the nodes along the pathof the network connection.

In step 1008, in response to the connection resize control signal ateach node along the path the allocated N tributary slots are added tothe M tributary slots already included in the network connection.Specifically, the N tributary slots are added to the M tributary slotswith respect to a link connection, a matrix through-connection, or both.For example, the N additional tributary slots may be added to a matrixconnection in a hitless manner to, i.e. may be added to a matrixconnection's ODTUk.M that carries the ODUflex. Such addition creates anODTUk.M+N and multiplies the C_(m) with a factor of M/(M+N) to reducethe C_(m) value (note that C_(n) does not change). Further, the Nadditional tributary slots allocated to a link connection are added in ahitless manner to the link connection's ODTUk.M that carries the ODUflexconnection. The addition creates an ODTUk.M+N and multiplies the C_(m)with a factor of M/(M+N) to reduce the C_(m) value (C_(n) does notchange). The incrementing of each matrix or link connection's ODTUk.Mcan be performed independent of the incrementing of any of the othermatrix/link connection's ODTUk.M.

The incrementing of the link connections may only be performed afterverifying (e.g., in the data plane) that both ends of the linkconnections have been configured equally, i.e. the same tributary slotsare connected at both ends (i.e. the N tributary slots are madeavailable in a synchronized manner between each pair of neighboringnodes along the network connection path). In one embodiment, theincrementing of the C_(m) waits until all link connections and matrixconnections are upgraded. Such waiting does not require managementcontrol/interactions in case the data plane performs this check (seeembodiments described below for further details). The ingress end nodestarts to increment the C_(m) value after having received anacknowledgement from the egress end node that all link connections havebeen resized. The egress determines this by inspecting the OH of theODTUk.ts.

Hitless incrementing of an ODTUk.M to a ODTUk.(M+N) (N≧1) requires thatthere is at least one M:(M+N) process (re-grouping process) available ineach of the intermediate nodes. This process is located between anODUflex link and an ODUflex matrix through-connection. The M:(M+N)process converts groups of M ODUflex bytes into groups of (M+N) ODUflexbytes, or vice versa. The process is active in a period when either alink connection occupies M tributary slots and the matrixthrough-connection occupies (M+N) tributary slots, or when a linkconnection occupies (M+N) tributary slots and the matrixthrough-connection occupies M tributary slots.

In step 1010, a transport data rate of the signal passing through thenetwork connection is increased, but only after the M+N tributary slotsare available for the network connection at each node along the path ina synchronized manner between each pair of neighboring nodes. Forexample, the bandwidth (bit rate) of an ODUflex signal expressed in thevalue of C_(m) is incremented in steps of 1 per ODTUk.M+N multiframe(C_(n) now changes also). The mapping processes at intermediate nodesfollow this incrementing immediately (this requires dedicated processingin the mapping components).

FIG. 11 illustrates in more detail a procedure for controlling dynamichitless resizing, in particular decrementing, a network connection in adata transport network. In step 1102, N of M tributary slots are marked.For example, the network management (or a control plane mechanism) maymark N tributary slots in each link connection endpoint of the ODUflexconnection 116 of FIG. 1 as “to be removed”. In step 1104, a connectionresize control signal is sent to each node along the path of the networkconnection.

In step 1106, by the ingress end node a data rate control signal is senthop-by-hop along the path of the network connection, wherein the datarate control signal is discarded by a node which has not finished thestep of adding or marking for removal, respectively, the N tributaryslots. In step 1108, the egress end node sends in response to areception of the data rate control signal an acknowledgement to theingress end node. After N tributary slots have been prepared for removalat each node along the path of the network connection in a synchronizedmanner between each pair of neighboring nodes, in step 1110, a transportdata rate of the signal passing through the network connection isdecreased by the ingress end node.

Eventually, in step 1112, in response to the connection resize controlsignal at each node along the path the marked N tributary slots areremoved from the M tributary slots. More specifically and with respectto an ODUflex example, the bandwidth (bit rate) of an ODUflex signalexpressed in the value of C_(m) is decremented in steps of 1 per ODTUk.Mmultiframe (C_(n) changes also); the mapping processes at intermediatenodes are adapted thereto, i.e. follow this decrementing immediately.Then, the N tributary slots within a link connection are removed in ahitless manner from the link connection's ODTUk.M that carries theODUflex. The removal creates an ODTUk.M−N. The C_(m) are multiplied witha factor of M/(M−N) to increase the C_(m) value (note that C_(n) doesnot change). The decrementing of the ODUflex link connection may only beperformed after verifying (e.g., in the data plane) that both ends ofthe link connections have been configured equally, i.e. the sametributary slots carry the ODUflex connection at both ends.

Additionally, the N tributary slots allocated to a matrixthrough-connection are removed in a hitless manner from the matrixconnection's ODTUk.M that carries the ODUflex connection. The removalcreates an ODTUk.M−N and multiplies the C_(m) with a factor of M/(M−N)to increase the C_(m) value (C_(n) does not change).

The decrementing of the ODUflex's C_(m) has to be performed before alink connection or matrix connection is resized. In case the data planeperforms this check, such waiting does not require managementcontrol/interactions. The decrementing of each matrix or linkconnection's ODTUk.M can be performed independent of the decrementing ofany of the other matrix/link connection's ODTUk.M. After the removal ofthe N slots, M−N tributary slots are available for the networkconnection at each node along the path.

With regard to the connection resize control signaling received by eachof the nodes along the path of the network connection in steps 1006 and1104, this signaling may be sent once per resize event to each node andmay comprise, for example, a connection ID indicating the networkconnection, an indication of whether to increase or decrease theconnection (and to which data rate or bandwidth), a list of thetributary slots to be added or removed, and, for each of the TS in thelist, a tributary port ID to which the particular slot is to be added orfrom which the particular slots is to be removed. No further networkmanagement operation is generally required.

FIG. 12 illustrates a format for in-band (data plane) link and matrixthrough-connection bandwidth resize control signaling (not to beconfused with the connection resize control signals received by eachnode from network management) and data rate control signaling to be usedfor controlling a dynamic hitless resizing of an ODUflex connection inan OTN, i.e. hitless ODUflex(GFP)/M increase and decrease. The in-bandconnection resize control signaling is required in order that twoneighboring nodes may inform each other on which links are currentlyactive during the resizing process in order to avoid that packets arelost (i.e. in order for the resizing being performed in hitless manner).The control may be mostly conveyed by in-band resize control overheadlocated in OPUk tributary slot overhead bytes.

Specifically, the overhead in column 15, rows 1, 2, 3 of OPUk tributaryslots can be used, namely of those slots which are either allocated asadditional tributary slots for an ODUflex(GFP) tributary port (in caseof incremental resize), or which are marked as tributary slots to beremoved from an ODUflex(GFP) tributary port (in case of decrementalresize). Thus, ODUflex Resize Control Overhead (RCOH) may be carried inthe OPUk Tributary Slot Overhead (TSOH) of the allocated, but not yetactive or removable, but not yet removed OPUk TSs.

This RCOH may support link and matrix connection (ODTUk.M) resizecontrol fields and ODUflex data rate (bit rate) resize control fields.The default value of all fields might be ‘0’. According to theembodiment illustrated in FIG. 12, the signaling parameters CTRL(Connection Control), TPID (Tributary Port ID), TSGS (Tributary SlotGroup Status), TSCC (Tributary Slot Connectivity Check) and NCS (NetworkConnection Status) might be used.

With regard to link and matrix through-connection resize control, theCTLR field is a 2-bit control field with NORM (11), ADD (01) and REMOVE(10) states and an IDLE (00) (unsourced) indication. The TPID field is a3(4)-bit (HO OPU2), 5(6)-bit (HO OPU3) and 7-bit (HO OPU4) TributaryPort ID field carrying the Tributary Port number to which the tributaryslot is to be added or from which the TS is to be removed. The 1-bittributary slot group status (TSGS) field with values ACK (1) and NACK(0) is generated by the sink (egress) to confirm to the source (ingress)that the tributary slots for addition or removal have been configuredalso at the sink end and that the sink end is ready to receive theincrease of the ODTUk.M in to the ODTUk.M+N, or decrease of the ODTUk.Minto the ODTUk.M−N, respectively.

After receipt of TSGS=OK, the ingress end node can change its ADD orREMOVE state to a NORM state and start the incrementing or decrementingprocess at the boundary of the next HO OPUk multiframe.

Data rate control acts for hitless incrementing/decrementing of theODUflex(GFP) signal bit rate expressed in C_(m). The 1-bit tributaryslot connectivity check (TSCC) signal, with a value of TSCC=1 isinserted by the first ODUkP/ODUj-21_A_So function and passed throughfrom ODUkP/ODUj-21_A_Sk function on the ingress port of an intermediatenode to the ODUkP/ODUj-21_A_So function on the egress port of that nodeuntil the signal is received by the last ODUkP/ODUj-21_A_Sk function.Such passing through between ingress and egress ports on intermediatenodes may be performed in hardware or in software. If a re-grouping orM:(M+N) process is active in the intermediate node, this process insertsTSCC=0 in the (M+N) direction. Only when the process is already removed,the value of the received TSCC bit is forwarded as it is.

When the TSCC=1 indication is received by the ODUflex(GFP) egress endnode (ODUkP/ODUj-21_A_Sk function) on all the N tributary slots, thenthe sink will acknowledge this receipt to the source via the 1-bitNetwork Connection Status (NCS). The source can then startincrementing/decrementing the ODUflex(GFP) C_(m) value, i.e. increase ordecrease, respectively, the ODUflex(GFP) signal. In the decrementingcase, the completion of the ODUflex(GFP) signal resize can be signaledby setting TSCC=0. Once TSCC=0 has passed through the intermediate nodesand is received by the last ODUkP/ODUj-21_A_Sk function, this functionwill acknowledge its receipt by setting NCS=0 (NACK).

FIGS. 13 a to 13 l schematically illustrate in some detail an embodimentof a process of hitlessly incrementing the ODUflex connection 116depicted in the foregoing figures. The boxes depict, from left to right,the ingress end node 102, the intermediate nodes 104 and 106, and theegress end node 108. FIG. 13 a illustrates an initial state of theODUflex (GFP) connection, according to which the connection is carriedby an ODTU2.2 between ingress end node 102 and intermediate node 104, anODTU 3.2 between the intermediate nodes 104 and 106, and another ODTU2.2between the intermediate node 106 and egress end node 108. Bottom arrowsdenote ODUflex link connection bandwidth control (in-band connectionresize control) signaling and ODUflex bit rate (data rate) controlsignaling, respectively. The connection bandwidth control signaling isconveyed hop-by-hop, while the bit rate control signaling can beconveyed in any way end-to-end. It is preferred that each of linkconnection bandwidth control as well as bit rate control is conveyed foreach TS which is to be added or removed.

FIG. 13 b is another illustration of a static situation (no resizing).Without any resizing going on, the resize control overhead in theunallocated OPUk tributary slots is carrying reserved bit values (e.g.,all ‘0’s). These default values will be interpreted as CTRL=IDLE,TPID=0, TSGS=NACK, TSCC=0 and NCS=NACK. The default values arerepresented by italic text and dashed lines in the figures. Normal textand solid lines indicate that the control parameters in the resizecontrol overhead are used, i.e. actively sourced. Bold text is intendedto indicate that the field carries a new value.

FIG. 13 c illustrates an initial state of the ODUflex hitless resizing.The intermediate node 104 is configured by network management connectionresize control to increase the ODTU2.2, the internal matrixthrough-connection, and the ODTU3.2 to intermediate node 106. FIG. 13 dshows that the matrix connection is resized in node 104. Both GMPs(Generic Mapping Point, also termed “Collection/Distribution FunctionCDP herein) of node 104 have been reconfigured from the status shown inFIG. 13 c with two matrix through-connections to the status shown inFIG. 13 d with three matrix through-connections associated with thenetwork connection 116.

Further, FIG. 13 d shows that the intermediate node 106 is instructed bynetwork management to increase the ODTU3.2, its internal matrixconnection and ODTU2.2 to egress end node 108 (network management mayinstruct all the nodes in arbitrary order and such instruction need notbe done in parallel). FIG. 13 e illustrates that the matrix connectionis resized in node 106. The egress end node 108 is instructed by networkmanagement to also increase the ODTU2.2, and to increase ODUflex(GFP)/2.

FIG. 13 f shows that the links between the nodes 104 and 106, andbetween 106 and 108 are resized. The corresponding CDPs (GMPs) of bothare thus dynamically re-configured to support three links instead ofonly two. Now the in-band bitrate resizing control fields can already bepassed through via node 106. FIG. 13 g shows that the ingress end node102 is configured to increase ODTU2.2 to intermediate node 104, and toincrease ODUflex (GFP)/2.

FIG. 13 h illustrates resizing of links between nodes 102 and 104. Theresize control overhead between nodes 104 and 106, and between 106 and108 goes back to default values. In-band bit rate control can be passedthrough along the entire path between end nodes 102 and 108. Accordingto FIG. 13 i, resize control overhead is back to default values alsobetween nodes 102 and 104. Based on bit rate control signaling,C_(n)/C_(m) modes are resized in the end nodes 102 and 108,respectively. The mapping processes (called Generic Mapping Processes,GMPs here) are configured to immediately respond to incoming C_(m)increments.

FIG. 13 j illustrates that ODUflex (GFP)/2 is incremented byincrementing the transmitted C_(n)/C_(m) modes in the end nodes. Theintermediate GMP processors follow the incrementing. FIG. 13 k showsthat the intermediate processors change their C_(n) to normal mode(n=8). FIG. 13 l shows the static state after resizing is finished: Theresized ODUflex (GFP)/3 is available and in use. The resize controloverhead is back to default values over the network connection.

FIGS. 14 a to 14 l illustrate, in a similar manner as FIGS. 13 a to 13l, details of an embodiment of a process of hitlessly decrementing theODUflex connection 116 of FIG. 1. An initial state of the ODUflex (GFP)connection may be as illustrated by FIG. 14 a.

FIG. 14 b illustrates that the intermediate node 104 is instructed todecrease the ODTU2.3 to ingress end node 102, the internal matrixthrough-connection, and the ODTU3.3 to intermediate node 106. Thepass-through mode for the resize control overhead is to be entered byintermediate node 104. In FIG. 14 c it is shown that node 106 isinstructed to decrease the ODTU3.3, the internal matrix connection andthe ODTU2.3. Resize connection control is to be passed through node 106.Further, ingress end node 102 is configured to decrease ODUflex (GFP)/3.

According to FIG. 14 d, the egress end node 108 is configured todecrease the ODTU2.3 and also the ODUflex (GFP)/3. The status in FIG. 14e is that the resizing C_(n)/C_(m) mode is entered. FIG. 14 fillustrates that the ODUflex (GFP)/3 is decremented to ODUflex (GFP)/2.In FIG. 14 g, the completion of the ODUflex (GFP) resizing is indicatedand the normal C_(n)/C_(m) mode is entered. In FIG. 14 h, the completionof the ODUflex (GFP) resizing is acknowledged.

According to FIG. 14 i, the passing through of the resize controloverhead is disabled. The link between nodes 102 and 104 is decremented.In FIG. 14 j, the matrix connection in node 106 is decremented. Theresize connection control goes back to default on the link 110 betweennodes 102 and 104. FIG. 14 k illustrates that the link (sub)connectionsbetween nodes 104 and 106, and between nodes 106 and 108 aredecremented. In FIG. 14 l, the matrix connection in node 104 isdecremented, the resize connection control overhead goes back to defaulton the links 112 and 114 between nodes 104 and 106, and nodes 106 and108, respectively. FIG. 14 m shows that the decrementing procedure iscompleted with ODUflex (GFP)/2 being supported by ODTU2.2, ODTU3.2 andODTU2.2 on links 110, 112 and 114, respectively.

The techniques proposed herein enable a hitless resizing of networkconnections in data transport networks with less complexity thancompared to the prior art such as VCAT/LCAS, for example. For resizing,the VCAT/LCAS technique comprises only adding or removing end-to-endlinks, i.e. a distribution/collection function is realized only at theend nodes of a connection, while according to the techniques proposedhere, multiple CDP functions are provided along the network connection,one in each end node and two in each intermediate node.

The proposed techniques require in-band signaling only which might usecurrently unused tributary slot overhead in case of ODUflex, i.e. noadditional signaling protocol needs to be implemented. The signaling isalso less complex than in the LCAS case. For example, there is no needto send back a status of each ODUflex slot back to the source.

Further, a minimum management overhead only is required, e.g. forallocating spare tributary slots in case of incrementing a networkconnection. Thus, there is much less associated state required in anetwork management plane then in ODUk VCAT/LCAS case. While the virtualconcatenation according to VCAT/LCAS requires the use of delaycompensating buffers at the egress end point of the network connection,there is no need for such buffer according to the techniques proposedherein.

While the current invention has been described in relation to itspreferred embodiments, it is to be understood that this description isfor illustrative purposes only. Accordingly, it is intended that theinvention be limited only by the scope of the claims appended hereto.

1. A method for controlling dynamic hitless resizing of a networkconnection in a data transport network, wherein a path of the networkconnection extends between two connection end nodes and optionally overone or more intermediate nodes of the data transport network; whereinthe network connection transports data of client services in transportframes from the ingress end node to the egress end node; and wherein thenetwork connection comprises a first set of M tributary slots defined ina payload area of a higher order transport scheme of the data transportnetwork; the method comprising the following steps, in case the networkconnection is to be incremented: receiving a connection resize controlsignal at each of the nodes along the path of the network connection;adding at each node along the path in response to the connection resizecontrol signal a second set of N tributary slots to the first set of theM tributary slots, such that the network connection comprises M+Ntributary slots; and increasing, after M+N tributary slots are availablefor the network connection at each node along the path and in asynchronized manner between each pair of neighboring nodes, a transportdata rate of the network connection; and in case the network connectionis to be decremented: receiving a connection resize control signal ateach of the nodes along the path of the network connection; decreasing,after a second set of N tributary slots has been prepared for removal ateach node along the path of the network connection in a synchronizedmanner between each pair of neighboring nodes, a transport data rate ofthe signal passing though the network connection; and removing at eachnode along the path in response to the connection resize control signala second set of N tributary slots from the first set of the M tributaryslots, such that the network connection comprises M−N tributary slots.2. The method according to claim 1, Wherein the network connectioncomprises a set of link connections between each pair of neighboringnodes along the path, and comprises matrix through-connections in eachintermediate node in the path, a matrix internally interconnectingmultiple links of the intermediate node with other nodes in the datatransport network, link connections and matrix through-connections beingdefined based on the tributary slots, wherein each node along the pathof the network connection comprises at least on collection/distributionpoint for either collecting the client data from a set of linkconnections and distributing the client data to a set of matrixthrough-connections or for collecting the client data from a set ofmatrix through-connections and distributing the client data to a set oflink connections; and wherein, in case the network connection is to beincremented, the step of adding the N tributary slots comprises, at thecollection/distribution point, adding the N tributary slots to the Mlink connections, and adding the N tributary slots to the M matrixthrough-collections; and wherein, in case the network connection is tobe decremented, the step of removing the N tributary slots comprises, atthe collection/distribution point, removing the N tributary slots fromthe M link connections, and removing the N tributary slots from the Mmatrix through-connections.
 3. The method according to claim 1,comprising the further steps of sending, by the ingress end node, a datarate control signal hop-by-hop along the path of the network connection,wherein the data rate control signal is discarded by a node which hasnot finished the step of adding or marking for removal, respectively,the N tributary slots; sending, by the egress end node in response to areception of the data rate control signal, an acknowledgement to theingress end node; and increasing, in case the network connection is tobe incremented, by the ingress end node, in response to the reception ofthe acknowledgement the data rate of the signal passing through thenetwork connection; or, in case the network connection is to bedecremented, decreasing the data rate of the signal passing through thenetwork connection and then removing the N tributary slots from the Mtributary slots at each node along the path.
 4. The method according toclaim 1, wherein the step of adding or removing, respectively, thesecond set of N tributary slots to or from the first set of the Mtributary slots in an intermediate node comprises adding or removing,respectively, the N tributary slots to or from the M tributary slotswith respect to at least one of a link connection and a matrixthrough-connection; and re-grouping, in case M tributary slots areassigned to the link connection and M+N tributary slots are assigned tothe matrix through-connection, or in case M+N tributary slots areassigned to the link connection and M tributary slots are assigned tothe matrix through-connection, the data to be transported over thenetwork connection from M data groups into M+N data groups or from M+Ndata groups into M data groups, or re-grouping, in case M tributaryslots are assigned to the link connection and M−N tributary slots areassigned to the matrix through-connection, or in case M−N tributaryslots are assigned to the link connection and M tributary slots areassigned to the matrix through-connection, the data to be transportedover the network connection from M data groups into M−N data groups orfrom M−N data groups into M data groups.
 5. The method according toclaim 1, wherein the step of adding the N tributary slots to the Mtributary slots in a node comprises decreasing a number of data unitsper transport frame for the M tributary slots by a factor of M/(M+N), oralternatively the step of removing the N tributary slots from the Mtributary slots in the node comprises increasing a number of data unitsper transport frame for the M tributary slots by a factor of M/(M−N). 6.The method according to claim 5, wherein a number of data units pertransport frame for the N tributary slots is kept unchanged.
 7. Themethod according to claim 5, wherein, in the step of increasing ordecreasing, respectively, the transport data rate of the networkconnection, a number of data units per transport frame is increased ordecreased, respectively, collectively for the M tributary slots and theN tributary slots.
 8. The method according to claim 1, wherein theconnection resize control signal is sent by network management inarbitrary order to each of the nodes along the path of the networkconnection, and wherein the step of adding or removing, respectively,the N tributary slots to or from the M tributary slots is performed ineach of the nodes along the network connection path independently. 9.The method according to claim 1, comprising, for the case that the Ntributary slots are to be added to the M tributary slots, the previoussteps of checking an availability of N tributary slots in each of thenodes along the path of the network connection; and allocating availableN tributary slots in the nodes along the path for the networkconnection.
 10. The method according to claim 1, wherein the connectionresize control signal and the data rate control signal are transportedin an overhead portion of at least one of the second set of the Ntributary slots.
 11. The method according to claim 1, wherein the datatransport network comprises an optical transport network and inparticular the network connection is an Optical Channel Data Unit “ODU”connection with selectable bandwidth, in particular an ODUflexconnection.
 12. A method for controlling dynamic hitless resizing of anetwork connection in a data transport network, wherein a path of thenetwork connection extends between two connection end nodes andoptionally over one or more intermediate nodes of the data transportnetwork; wherein the network connection transports data of clientservices in transport frames from the ingress end node to the egress endnode; and wherein the network connection comprises a first set of Mtributary slots defined in a payload area of a higher order transportscheme of the data transport network; the method being performed in theingress end node and comprising the following steps, in case the networkconnection is to be incremented: receiving a connection resize controlsignal; adding a second set of N tributary slots to the first set of theM tributary slots; and increasing, after M+N tributary slots areavailable for the network connection at each node along the path and ina manner synchronized with the downstream node, a transport data rate ofthe signal passing through the network connection; and in case thenetwork connection is to be decremented: receiving a connection resizecontrol signal; decreasing, after a second set of N tributary slots hasbeen prepared for removal in a synchronized manner between the ingressend node and the neighboring node, a transport data rate of the networkconnection; and removing a second set of N tributary slots from thefirst set of the M tributary slots.
 13. The method according to claim12, comprising the further steps of initiating a sending of a data ratecontrol signal hop-by-hop along the path of the network connection,wherein the data rate control signal is discarded by a node which hasnot finished the step of adding or marking for removal, respectively,the N tributary slots; receiving an acknowledgement to the data ratecontrol signal from the egress end node; and increasing, in case thenetwork connection is to be incremented, in response to the reception ofthe acknowledgement the data rate of the signal passing through thenetwork connection; or, removing, in case the network connection is tobe decremented, the N tributary slots from the M tributary slots.
 14. Amethod for controlling dynamic hitless resizing of a network connectionin a data transport network, wherein a path of the network connectionextends between two connection end nodes and optionally over one or moreintermediate nodes of the data transport network; wherein the networkconnection transports data of client services in transport frames fromthe ingress end node to the egress end node; and wherein the networkconnection comprises a first set of M tributary slots defined in apayload area of a higher order transport scheme of the data transportnetwork; the method being performed in an intermediate node andcomprising the steps of: receiving a connection resize control signal;adding or removing, respectively, in response to the connection resizecontrol signal a second set of N tributary slots to or from the firstset of the M tributary slots, such that the network connection comprisesM+N tributary slots or M−N tributary slots, respectively.
 15. The methodaccording to claim 14, wherein the network connection comprises a set oflink connections between each pair of neighboring nodes along the path,and comprises matrix through-connections in each intermediate node inthe path, a matrix internally interconnecting multiple link connectionsof the intermediate node with other nodes in the data transport network,link connections and matrix through-connections being defined based onthe tributary slots, wherein the intermediate node comprises a firstcollection/distribution point for collecting the client data from a setof link connections terminating from the upstream node and distributingthe client data to a set of matrix through-connections and a secondcollection/distribution point for collecting the client data from theset of matrix through-connections and distributing the client data to aset of link connections starting towards a downstream node; and wherein,in case the network connection is to be incremented, the step of addingthe N tributary slots comprises, at each of the collection/distributionpoints, adding the N tributary slots to the M link connections, andadding the N tributary slots to the M matrix through-collections; andwherein, in case the network connection is to be decremented, the stepof removing the N tributary slots comprises, at each of thecollection/distribution points, removing the N tributary slots from theM link connections, and removing the N tributary slots from the M matrixthrough-connections.
 16. The method according to claim 14, comprisingthe further steps of receiving a data rate control signal from a nodeupstream or downstream the network connection path; and discarding thedata rate control signal in case the step of adding or marking forremoval, respectively, the N tributary slots is not finished, orforwarding the data rate control signal to the next node along thenetwork connection path.
 17. The method according to claim 14, whereinthe step of adding or removing, respectively, the N tributary slots toor from the M tributary slots comprises adding or removing,respectively, the N tributary slots to or from the M tributary slotswith respect to either a link connection, the link connection connectingthe intermediate node with another node along the path of the networkconnection, or a matrix through-connection, the matrix internallyinterconnecting multiple link connections of the intermediate node withother nodes in the data transport network; and re-grouping, in case Mtributary slots are assigned to the link connection and M+N tributaryslots are assigned to the matrix through-connection, or in case M+Ntributary slots are assigned to the link connection and M tributaryslots are assigned to the matrix through-connection, the data to betransported over the network connection from M data groups into M+N datagroups or from M+N data groups into M data groups, or re-grouping, incase M tributary slots are assigned to the link connection and M−Ntributary slots are assigned to the matrix through-connection, or incase M−N tributary slots are assigned to the link connection and Mtributary slots are assigned to the matrix through-connection, the datato be transported over the network connection from M data groups intoM−N data groups or from M−N data groups into M data groups.
 18. A methodfor controlling dynamic hitless resizing of a network connection in adata transport network, wherein a path of the network connection extendsbetween two connection end nodes and optionally over one or moreintermediate nodes of the data transport network; wherein the networkconnection transports data of client services in transport frames fromthe ingress end node to the egress end node; and wherein the networkconnection comprises a first set of M tributary slots defined in apayload area of a higher order transport scheme of the data transportnetwork; the method being performed in the egress end node andcomprising the steps of: receiving a connection resize control signal;adding or removing, respectively, in response to the connection resizecontrol signal a second set of N tributary slots to or from the firstset of the M tributary slots, such that the network connection comprisesM+N tributary slots or M−N tributary slots, respectively; receiving adata rate control signal from the node upstream the network connectionpath; and sending, in response to the reception of the data rate controlsignal, an acknowledgement to the ingress end node.
 19. A computerprogram product comprising program code portions for performing themethod according to any one of the preceding claims when the computerprogram product is executed on one or more computing devices.
 20. Thecomputer program product of claim 19, stored on a computer readablerecording medium.
 21. A network node for controlling dynamic hitlessresizing of a network connection in a data transport network, wherein apath of the network connection extends between two connection end nodesand optionally over one or more intermediate nodes of the data transportnetwork; wherein the network connection transports data of clientservices in transport frames from the ingress end node to the egress endnode; and wherein the network connection comprises a first set of Mtributary slots defined in a payload area of a higher order transportscheme of the data transport network; the network node implementing theingress end node, comprising: a component configured to receives aconnection resize control signal; a component configured to add a secondset of N tributary slots to the first set of the M tributary slots; acomponent configured to increase, after M+N tributary slots areavailable for the network connection at each node along the path and ina synchronized manner between each pair of neighboring nodes, atransport data rate of the network connection; a component configured todecrease a transport data rate of the network connection, after a secondset of N tributary slots has been prepared for removal at each nodealong the path of the network connection in a synchronized mannerbetween each pair of neighboring nodes; and a component configured toremove a second set of N tributary slots from the first set of the Mtributary slots.
 22. The network node according to claim 21, furthercomprising a component configured to initiate a sending of a data ratecontrol signal hop-by-hop along the path of the network connection,wherein the data rate control signal is discarded by a node which hasnot finished the step of adding or marking for removal, respectively,the N tributary slots; a component configured to receive anacknowledgement to the data rate control signal from the egress endnode; and a component configured to increase, in response to thereception of the acknowledgement, the data rate of the signal passingthrough the network connection, and a component configured to decrease,in case the network connection is to be decremented, the data rate ofthe signal passing through the network connection; and a componentconfigured to remove, in case the network connection is to bedecremented, N tributary slots from the M tributary slots.
 23. A networknode for controlling dynamic hitless resizing of a network connection ina data transport network, wherein a path of the network connectionextends between two connection end nodes and optionally over one or moreintermediate nodes of the data transport network; wherein the networkconnection transports data of client services in transport frames fromthe ingress end node to the egress end node; and wherein the networkconnection comprises a first set of M tributary slots defined in apayload area of a higher order transport scheme of the data transportnetwork; the network node implementing an intermediate node, comprising:a component configured to receive a connection resize control signal; acomponent configured to add or remove, respectively, in response to theconnection resize control signal a second set of N tributary slots to orfrom the first set of the M tributary slots, such that the networkconnection comprises M+N tributary slots or M−N tributary slots,respectively; and a component configured to forward the connectionresize control signal to the next node along the network connectionpath.
 24. The network node according to claim 23, wherein the networkconnection comprises a set of link connections between each pair ofneighboring nodes along the path, and comprises matrixthrough-connections in each intermediate node in the path, a matrixinternally interconnecting multiple link connections of the intermediatenode with other nodes in the data transport network, link connectionsand matrix through-connections being defined based on the tributaryslots, wherein the intermediate node comprises a firstcollection/distribution point for collecting the client data from a setof link connections terminating from the upstream node and distributingthe client data to a set of matrix through-connections and a secondcollection/distribution point for collecting the client data from theset of matrix through-connections and distributing the client data to aset of link connections starting towards a downstream node; and whereineach of the collection/distribution points is configured to, in case thenetwork connection is to be incremented, add the N tributary slots byadding the N tributary slots to the M link connections, and adding the Ntributary slots to the M matrix through-collections; and is configuredto, in case the network connection is to be decremented, remove the Ntributary slots by removing the N tributary slots from the M linkconnections, and removing the N tributary slots from the M matrixthrough-connections.
 25. The network node according to claim 23, furthercomprising a component configured to receive a data rate control signalfrom a node upstream or downstream the network connection path; acomponent configured to discard the data rate control signal in case thestep of adding or removing, respectively, the N tributary slots is notfinished, and a component adapted to forward the data rate controlsignal to the next node along the network connection path.
 26. Thenetwork node according to claim 23, wherein the component configured toadd or remove, respectively, the N tributary slots to or from the Mtributary slots comprises a sub-component configured to add or remove,respectively, the N tributary slots to or from the M tributary slotswith respect to either a link connection, the link connection connectingthe intermediate node with another node along the path of the networkconnection, or a matrix through-connection, the matrix internallyinterconnecting multiple link connections of the intermediate node withother nodes in the data transport network; and a sub-componentconfigured to re-group, in case M tributary slots are assigned to thelink and M+N tributary slots are assigned to the matrixthrough-connection, or in case M+N tributary slots are assigned to thelink connection and M tributary slots are assigned to the matrixthrough-connection, the data to be transported over the networkconnection from M data groups into M+N data groups or from M+N datagroups into M data groups, or configured to re-group, in case Mtributary slots are assigned to the link connection and M−N tributaryslots are assigned to the matrix through-connection, or in case M−Ntributary slots are assigned to the link connection and M tributaryslots are assigned to the matrix through-connection, the data to betransported over the network connection from M data groups into M−N datagroups or from M−N data groups into M data groups.
 27. A network nodefor controlling dynamic hitless resizing of a network connection in adata transport network, wherein a path of the network connection extendsbetween two connection end nodes and optionally over one or moreintermediate nodes of the data transport network; wherein the networkconnection transports data of client services in transport frames fromthe ingress end node to the egress end node; and wherein the networkconnection comprises a first set of M tributary slots defined in apayload area of a higher order transport scheme of the data transportnetwork; the network node implementing the egress end node, comprising:a component configured to receive a connection resize control signal; acomponent configured to add or remove, respectively, in response to theconnection resize control signal a second set of N tributary slots to orfrom the first set of the M tributary slots, such that the networkconnection comprises M+N tributary slots or M−N tributary slots,respectively; a component configured to receive a data rate controlsignal from the node upstream the network connection path; and acomponent configured to send, in response to a reception of the datarate control signal, an acknowledgement to the ingress end node.